The inscription indicating that Lachlan Macquarie was a Lieutenant Colonel in the 86th. Regiment, is somewhat misleading. Lachlan Macquarie had been commissioned as a Major in the 86th. Regiment of Foot on 15 January 1801, and served with it throughout the campaign in Egypt in 1801-1802, with the local or brevet rank of 'Lt. Colonel' while serving as Deputy Adjutant-General to General David Baird (1757-1829), commander of the Indian expeditionary army in Egypt. In the period 1803-1804, during his return to Britain, Macquarie was appointed as Assistant-Adjutant-General to the London District; however, he still only possessed an effective majority in the 86th. Regiment. And despite his pleadings with the Commander-in-Chief, the Duke of York, for promotion, he was forced to return to India, achieving only a commitment from the Duke [on 15 March] that:
"he would avail himself of the first favorable opportunity of Promoting me ! – Upon this I took my leave of H. R. Highness, having, upon the whole, no just reason to be dissatisfied with my reception. —"
This was the extent of his guarantee for receiving a commission as a Lieutenant Colonel; and consequently, the name plate inscription on the travelling desk must be seen more as an indication of local brevet rank within India. As such, it was more a statement of intent than as a description of an effective rank within the 86th. Regiment.
A promotion prior to Macquarie's return to India would have allowed him to seek an immediate exchange from the 86th. Regiment in India into another regiment in Britain, and the Duke was determined that, in the short term at least, Macquarie should suffer a 'temporary exile'. The Commander-in-Chief waited until Macquarie was in Bombay again, and then gave him effective advancement to command the 73rd. Regiment, which by this stage had already returned to Britain. Macquarie had to wait until 25 October 1805 before he received any intimation of his official promotion:
"I took up the Madras Newspaper of the 12th. Instant, and in reading it over was most agreeably surprised to find in it that I have been lately Promoted at Home to the Effective Lieut. Colonelcy of the 73d. Regiment, vacant by the death of the Hon'ble Colonel St. John! – I stumbled by mere accident upon this piece of good news – being the first and only intimation I have yet had of this most gratifying and highly flattering mark of my most gracious Sovereign's approbation and reward of my Services!"
However, Macquarie could not leave the 86th. Regiment while it was still on active service against the Marathas in 1805-1806, and furthermore, he was compelled to wait until the official notification of the gazetting of his commission reached India, in 1806. This delay would become a source of friction and misunderstanding between Macquarie and his fiancée, Elizabeth Campbell of Airds, who was awaiting his return after accepting his proposal of marriage in March 1805. Macquarie did not return to Britain again until October 1807, and married Elizabeth on 3 November 1807.